FIG. 1 is a schematic block diagram of a conventional photovoltaic device. A photovoltaic device 10 can typically have one or more solar cells 12 disposed within it. A solar cell conventionally is made by having a semiconductor junction disposed between a layer of conducting material 104 and a layer of transparent conducting material 110. Light impinges upon the solar cells 12 of a photovoltaic module 10 and passes through the transparent conducting material layer 110. Although other designs are possible, a typical semiconductor junction comprises an absorber layer 106 and a window layer 108. Within the semiconductor junction, the photons interact with the material to produce electron-hole pairs. The semiconductor junction is typically doped creating an electric field extending from the junction layer. Accordingly, when the holes and/or electrons are created by the sunlight in the semiconductor junction, they will migrate depending on the polarity of the field either to the transparent conducting material layer 110 or the layer of conducting material 104. This migration creates current within the solar cell 12 that is routed out of the cell for storage and/or concurrent use.
One conducting node of the solar cell 12 is shown electrically coupled to an opposite node of another solar cell 12. In this manner, the current created in one solar cell may be transmitted to another, where it is eventually collected. The currently depicted apparatus in FIG. 1 is shown where the solar cells are coupled in series, thus creating a higher voltage device. In another manner, not shown, the solar cells can be coupled in parallel thereby increasing the resulting current rather than the voltage.
As further illustrated in FIG. 1, the conducting material 104 is supported by a substrate. Further, an antireflection coating 112 may be disposed on transparent conducting material 110. Solar cells 12 are sealed from the environment by the substrate 102 and the transparent panel 60. Typically, there is a filler layer 5 between the active layers of the solar cell and the transparent panel 60. In some solar cells, there is a filler layer between the conducting material 104 and the substrate 102. Typically, this filler layer is made of ethylene-vinyl acetate (EVA). The EVA is applied as a sheet then heated so that it melts and crosslinks. In this manner, an intermediate layer is formed between the device (layers 104 through 112) and the outer layers 60 and 102. The cured EVA is solid in nature, and has a very low volumetric coefficient of expansion relative to temperature. Accordingly, the EVA is very tolerant in the environment. However, it is hard to apply the EVA in anything other than planar sheets. Thus, for assemblies that are not planar in nature, the application of the EVA is problematic. Further, since the vast majority of solar cells are employed as planar cells, there really is no outstanding need to alter the outer-layer—EVA—device architecture.
Given the above background, what is needed in the art are improved filler layers for photovoltaic devices that can be easily assembled even in the case where the photovoltaic device is based upon a non-planar substrate. Further, what is needed in the art are photovoltaic devices that incorporate such improved filler layers.
Like reference numerals refer to corresponding parts throughout the several views of the drawings. Dimensions are not drawn to scale.